AS physics help motion i think

im doin some coursework for AS physics and need help with a practical experiment.
It seems simple enough... rolling a trolly down a ramp and calculating the speed of the trolley after one meter. The variable we change is the steepness of the ramp (so the angle from the floor) and so we need to do a graph and work out the trend between the speed and the angle

problem is my results are pretty dodgy and i cant really get a clear trend apart from that if you increase the angle the speed is increased, which is pretty obvious

what sort of trends SHOULD i expect and why???

at the moment i have got a kind of curve (i think) because i have said changing the angle changes the vertical distance and v^2= u^2+2as so the vertical distance is proportional to the speed squared so its a curve, right?- but i dont think that is right because its the angle im looking at not just the height and theres all sines and stuff i have to worry about